Nuclear Magnetic Resonance and Order Fluctuations in the Isotropic Phase

Pretransitional dynamics in the isotropic phase of nematics was also studied by other optical methods. Wong and Shen [74, 75], Flytzanis and Shen [76] and Prost and Lalanne [77] have used the optical Kerr effect to induce nematic ordering in the isotropic phase. Using a Q-switched laser they could measure the relaxation time of the induced birefringence. They found a good agreement with the Landau-de Gennes theory (see Fig. 5) and with the results of Stinson and Litster. 

There are other reports on the study of pretransitional dynamics in polymeric and lyotropic nematics. Quantitative measurements of ratios of Frank elastic constants and Leslie viscosities in the pretransitional range of poly-y-benzyl-glutamate polymeric nematic are reported by Taratuta et al. [85]. McClymer and Keyes [86-88] report light scattering studies of pretransitional dynamics of potassium laurate-decanol-D20 system. An interesting study of a magnetic-field induced I N phase transition in a colloidal suspension is reported by Tang and Fraden [89]. 

4 Nuclear Magnetic Resonance and Order Fluctuations in the Isotropic Phase 

The first NMR evidence of large fluctuations in the magnitude of the nematic order parameter tensor in the isotropic phase above has been obtained by the line-width measurements at 3 MHz in PA A [90]. As Tc is approached from above the line- 

A similar study has been performed in MBBA by Dong et al. [93]. The dispersion of the proton in the isotropic phase of 5CB, PAA and MBBA has been precisely studied by the field cycling technique by Noack and coworkers [94-96]. 

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Quasielectric Light Scattering and Order Fluctuations in the Isotropic Phase 174 Nuclear Magnetic Resonance and Order Fluctuations in the Isotropic Phase. 175 Quasielastic Light Scattering and Orientational Fluctuations below Tc. . . 177 Nuclear Magnetic Resonance and Orientational Fluctuations below Tc.. .. 177 Optical Kerr Effect and Transient Laser-Induced Molecular Reorientation.. 181... 

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